Well, considering you have a limited amount of ice types available at the point you get Vanilluxe, I'd say it's highly useful. Sure you can Poke Transfer, but not everyone has that option available to them. And not every Gen 1-4 Pokemon has been brilliant either.

Every generation has its downsides, I mean, remember this ******? Interesting design, but not handy in a battle really.

Access to spore, baton pass, and ANY other moves in the game..? Not that bad for team support if you ask me, but that's just my opinion. I'm sure there's a hundred ways to bring it down before it gets some serious setup time. Oh who am i kidding i just have a soft spot for Smeargle.

Yeah they're pretty squishy, but if you're using it to set up a substitute and baton pass off that and a stat boost it helps with survivability, but it does require some tough EV training to get its speed up to useful levels.